Kobyashevite

Chemical formula: Cu²⁺₅(S⁶⁺O₄)₂(OH)₆·₄H₂O

Kobiashevite is a rare, secondary copper mineral characterized by its distinctive turquoise color, forming delicate, acicular crystals.

## Characteristics Kobiashevite is a hydrated copper hydroxyl sulfate belonging to the devilline group. It occurs as very small, acicular or bladed crystals, which often form radial aggregates, rosettes, or crusts. Its delicate structure and vivid blue-green to turquoise color make it visually recognizable, despite the small size of its crystals. ## Physical Properties This mineral is characterized by a relatively low hardness of 2.5 on the Mohs scale, making it very susceptible to scratching. It is transparent and has a vitreous luster. Its density is approximately 3.16 g/cm³, which is typical for secondary copper minerals. ## Colors and Varieties Kobiashevite occurs in shades from blue-green to turquoise. Its color is uniform, and no named color varieties or commercial varieties are known. ## History and Name The mineral was named in honor of the Russian mineralogist and collector, Vyacheslav Yurievich Kobiashev (born 1958), in recognition of his contributions to the mineralogy of the Urals. It was officially approved by the International Mineralogical Association (IMA) in 2011. The type locality, from which this mineral was first described, is the Kapitalnaya mine in the Vishnevye Gory region of the Urals, Russia. ## Uses Due to its rarity, small crystal size, and delicacy, kobiashevite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals or secondary minerals from oxidation zones.

Properties

Mohs hardness: 2.5
Luster: Vitreous
Streak: Pale bluish green
Density: 3.16
Cleavage: {010}
Fracture: Step-Like
Transparency: Transparent
Crystal system: Triclinic

Diagnostic features

## Identification Kobiashevite can be identified by its characteristic turquoise color, acicular crystal habit, and the formation of radial aggregates. Its occurrence in the oxidation zones of copper deposits, often in association with other secondary copper sulfates, is also key. Reaction with acids is a confirming feature but destroys the sample. ## Distinguishing from Similar Minerals Kobiashevite is sometimes confused with other blue and green secondary copper minerals. From devilline and serpierite, to which it is closely related, it is often distinguished by a lighter, more turquoise hue and specific crystallographic features, identifiable only by advanced research methods. It may also resemble brochantite or aurichalcite, but differs from them in crystal habit – brochantite usually forms thicker needles, and aurichalcite has a pearly luster and often a lighter color. ## Crystal Forms Kobiashevite crystals are very small, acicular or thin-platy, elongated along the crystallographic axis. They typically form radial or stellate aggregates, as well as thin crusts and coatings on the host rock.

Geological environment

## Genesis Kobiashevite is a secondary mineral, formed in the oxidation zones (so-called iron caps) of copper ore deposits. It forms as a result of the weathering of primary copper sulfides, such as chalcopyrite, in the presence of sulfate-rich water. It forms under low temperature and pressure conditions, often in voids and fissures in rocks. ## Mineral Associations This mineral co-occurs with other secondary minerals of the oxidation zone. At the type locality (Kapitalnaya mine), it was found in association with gypsum, jarosite, chalcanthite, brochantite, malachite, azurite, as well as rarer minerals such as devilline, serpierite, posnjakite, and wroewolfeite. ## Localities The most important and best-documented occurrence of kobiashevite is its type locality – the Kapitalnaya mine in the Vishnevye Gory, Chelyabinsk Oblast, Urals, Russia. In addition, its presence has been noted in several other locations worldwide, including mines in the Lavrion region of Greece and the Jáchymov mine in the Czech Republic, which are known for their abundance of rare secondary minerals.

Rarity

Very rare

For collectors

## Quality Criteria The most prized kobiashevite specimens by collectors are those with well-formed, rich aggregates of acicular crystals of intense, turquoise color. Contrast with the rock matrix and the absence of damage to the delicate crystals are important. Due to the microscopic size of the crystals, the aesthetics of the entire cluster (aggregate) is crucial. The presence of rare associated minerals can further increase the value of the specimen. ## Popular Localities By far, the most sought-after specimens come from the type locality, the Kapitalnaya mine in the Urals, Russia. Specimens from this location are considered exemplary for this mineralogical species.

Care and storage

## Cleaning Kobiashevite specimens should be cleaned with the utmost care. Due to its low hardness and delicate crystalline structure, only gentle brushing with a soft brush is recommended to remove dust. The use of water is risky, as the mineral is soluble in acids and can react with impurities in water. If liquid is necessary, only pure isopropyl alcohol or distilled water should be used, applied very carefully and the specimen immediately dried with a stream of compressed air. ## What to Avoid Contact with acids, which will quickly dissolve the mineral, must be absolutely avoided. It should be protected from high temperatures, which can lead to dehydration and structural damage. Avoid ultrasonic cleaners, steam cleaning, and all chemical agents. The mineral is very brittle, so impacts and vibrations should be avoided. ## Storage Kobiashevite should be stored in stable conditions, away from heat sources and direct sunlight. It is best kept in a closed, padded "micromount" box to protect it from mechanical damage and dust. It should not be stored loosely with harder minerals.

External references

https://www.mindat.org/min-42367.html